This invention relates to a brake system for automotive vehicles having a brake pressure transmitter which is linked to the wheel brakes through pressure medium lines. Sensors are provided at the individual wheels or at wheels grouped together for the direct or indirect detection of the brake performance, that is of the braking effect or of the brake pressure. Controllable separating valves located in one or several of the pressure medium paths leading to the wheel brakes shut off the flow of pressure medium in one switching position.
It is known and customary and even legally prescribed in many countries to subdivide the pressure medium path from the brake pressure transmitter to the individual wheel brakes into two or several hydraulically separated brake circuits. This is done so that at the most only a part of the brake system fails in case of rupture of a line or in case of a leakage. In that event, the failure of the relevant brake circuit is indicated by a float or similar means through the drop of the fluid level in the fluid reservoir or in a compartment of that reservoir. Thus, the driver does not continue driving with the defective brake system and the reduced braking effect but rather to the nearest service station.
Depending on the number and location (i.e., front or rear axle) of the wheel brakes involved, dangerous situations may result due to the alteration and reduction of the braking effect caused by the defect. This is because the stopping distance becomes longer or because the driving stability may be jeopardized because of nonuniform braking effect. Although the negative effects of a leak would be reduced by hydraulically separated paths leading to each individual wheel brake, a solution to the problem is limited in practice to the realization of two or maximum three brake circuits because of the manufacturing efforts and expenditure involved. Thus, the brakes at several vehicle wheels may nevertheless fail simultaneously even in the latter case, notwithstanding such efforts and expenditure. To link each wheel or wheel brake to two brake circuits which are separated from each other hydraulically is prior art solution which, again, is highly expensive and leads to a dangerous reduction of the braking effect in the event of failure of one circuit.
It is, therefore, an object of the present invention with simple means and minor manufacturing efforts to limit the consequences of a leak in the pressure medium path, of the rupture of a line or of a defect of similar type to one wheel or to as few wheels possible.